Most people are just jumping into jailbreaking without looking through the other threads... IF YOU JAILBREAK YOUR IPHONE 4, YOU WILL LOSE THE ABILITY TO USE FACETIME AND MMS UNTIL THERE IS A FIX. EDIT: Okay, not for EVERYBODY, but many people are reporting it, including myself. Don't believe me? Search "MMS" or "FaceTime" in Twitter. EDIT 2: I managed to get it working... Hope it works for you!